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C803D Alternator Troubleshooting Guide C.E. Niehoff & Co.

CONTENTSSection A: Description and Operation ..............................2 Section B: Basic Troubleshooting ....................................5Section C: Advanced Troubleshooting ............................6

Battery Charging ConditionsThe following conditions may be observed during cold-start voltage tests until temperatures of electrical system components stabilize. The time it takes to reach optimum voltage and amps will vary with engine speed, load, and ambient temperature.

Maintenance/Low Maintenance Lead-Acid Battery:Traditional lead acid batteries require lowest charge volt-age of all vehicle battery chemistries. Battery cells must be maintained by periodically topping off with distilled water as required.

Maintenance-free Lead-Acid Battery:Maintenance-free batteries are similar to Maintenance/Low Maintenance batteries, but may require slightly higher charge voltage.

Deep-cycle/Marine Maintenance-free Battery:Charge acceptance of these batteries may display charac-teristics similar to maintenance-free batteries and may charge faster due to generally lower capacity relative to size.

AGM (Absorbed Glass Mat) Maintenance-free Battery:These dry-cell batteries respond better than standard maintenance-free batteries. If battery state of charge (SOC) drops to 75% or less, batteries should be recharged to 95% or higher separately from engine charg-ing system to avoid damaging charging system components and to provide best overall performance. Charge acceptance of these batteries may display charac-teristics similar to maintenance batteries, but may require higher charge voltage and will draw significant current (

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Section A: Description and Operation

Figure 3: C803D Alternator with Regulator Wiring Diagram

(See alternator specific characteristics drawing for notes and detailed descriptions)

C803D Alternator Description and Operation

C803D is a negative ground, cradle mount alternator rated at 28V/525A. C803D is internally rectified, and all windings and current-conducting components are non-moving, so there are no brushes or slip rings to wear out.

Voltage regulator is activated when regulator IGN ter-minal receives an ignition/energize signal from the vehicle, usually via oil pressure switch or multiplex sys-tem (see page 3 for regulator features). The regulator monitors alternator shaft rotation and provides field current only when it detects the alternator shaft rotating at a suitable speed.

After the regulator detects shaft rotation, it gradually applies field current, preventing an abrupt mechanical load on accessory drive system. Soft start may take up to 20 seconds after rotation and energize signals are sensed.

Refer to Figure 1 for alternator terminal locations . Refer to Figure 2 for alternator-to-regulator harness pin designations.

Figure 1: C803D Alternator Terminals

Figure 2: Alternator-to-Regulator Harness Pin Designations

Alternate Regulator Mounting Location

Voltage regulator

B+ Terminal

B‒ Terminal

Battery Cable Clamp

(optional)

A = Not UsedB = Not UsedC = B-D = B+E = PhaseF = F+

(SMART REGULATOR ONLY)

REGULATOR

THERMALSWITCH

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Section A: Description and Operation (cont)

Voltage RegulatorDescription and Operation

CEN voltage regulators can be mounted directly on alternator housing or remotely with compatible extension harness1. Regulator features include:

• IGN terminal/pin (required): Vehicle must supply battery volt-age to IGN terminal to energize charging system.

• D+ output terminal/pin (optional): D+ circuit supplies DC bat-tery voltage for use with charge indicator light or multiplex charge warning input.

• Phase output (optional): Phase terminal/pin taps AC voltage from alternator phase for use with relay or tachometer. Out-put is typically half of the output voltage at a frequency ratio of 10:1 of alternator speed.

• Adjustable voltage set points (See Table 1 below).

• Over-voltage cut out (OVCO): Regulator shuts off field switching circuit if it senses 32 volts or higher for 3 seconds or longer.

CEN Smart Regulator features also include:

• J1939 communication via 10 pin connector.

• Temperature compensation (optional): When used with com-patible CEN remote harness or sensor2, regulator will opti-mize voltage setting based on battery chemistry and com-partment temperature (See Table 1 below).

• Remote voltage compensation (optional): When used with compatible CEN remote harness or sensor2, regulator will boost voltage to batteries up to one volt over set point as nec-essary to compensate for resistive output cable losses.

• Parallel operation (optional): Alternator can be used in tan-dem with another compatible CEN alternator and will sync output when interconnected by A9-4045 harness or similar2.

• Charging system status LED indicator (see Table 2 on page 4). Figure 4: CEN Voltage Regulator Features

Alternator-to-regulator harness connector

J1939/temp/voltage harness connector

(Smart Regulator only)

IGN Terminal

D+ Terminal

P Terminal

Diagnostic LED

Voltage Select Switch

Table 1: Regulator Voltage Switch Settings

Position Conventional Regulator Set Point orSmart Series with Sensor/Harness Not ConnectedBattery profile for Smart Series Regulators with Sensor/Harness Connected (Battery Select)2,3

1 27.5 V Maintenance (D category)2 28.0 V Maintenance-free (Group 31)3 28.5 V AGM4 29.0 V Flat

1. Contact CEN for regulator extension harness options.2. Contact CEN for sensor/harness options

IGN/D+/P connector

(A2-399 only)

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Section A: Description and Operation (cont)

Regulator Status LED

Table 2: Regulator LED IndicationsLED COLOR ALTERNATOR / REGULATOR STATUS REQUIRED ACTION

GREEN (Solid)

Alternator and regulator operating normally.

No action required.

GREEN(Flashing)

Surge suppression circuit disabled; alterna-tor still charging battery.

No action required.

AMBER (Solid)

Voltage is below 25.0 V If voltage is at or below regulator setpoint, allow charg-ing system to operate for several minutes to normalize operating temperature. If charge voltage does not in-crease within 10 minutes, go to Chart 1 on page 6.

AMBER(Flashing)

No rotation detected. Power down and restart alternator. If LED remains flashing amber, perform troubleshooting procedures on page 6.

RED(Solid)

Field coil out of specification. Power down and restart alternator. If LED remains solid red, perform troubleshooting procedures on page 6.

RED(Flashing)

OVCO condition detected. Power down and restart alternator. If LED remains flashing red, refer to OVCO troubleshooting procedure on page 5.

NOTE: LED off = No power/output.

Figure 5: Regulator Status LED Location

Temperature/Voltage Sense/J1939 Harness Troubleshooting (if equipped on vehicle)To verify temperature sense function of temperature/voltage sense harness: Apply a warm air source (such as a hair dryer, not to heat above 120°F) to battery negative terminal of harness. B+ battery voltage should decrease as temperature increases. If voltage does not decrease: Check for a resistance reading of 5-15K Ohms across pin H in 10-pin connector on T-VS/J1939 harness and ground with meter in K Ohm scale.

Then check for battery voltage across pin J on temperature/voltage sense harness and ground with meter in VDC scale. If one or both readings fail, verify proper terminal connections on B+ and B− terminal leads from T-VS/J1939 harness. If both terminal connections are good, entire harness is defective and should be replaced.

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Basic Troubleshooting1. Inspect charging system components for damage.

Check connections at B– cable, B+ cable, and regulator harness. Check regulator terminal wiring from regulator to vehicle components. Repair or replace any damaged component before electrical troubleshooting.

2. Inspect vehicle battery connections. Connections must be clean and tight.

3. Inspect belt for wear and condition.

Preliminary Check-outCheck symptoms in Table 3 below and correct if necessary.

Required Tools and Equipment

Identification RecordEnter the following information in the spaces provided for identification records.

Alternator model number:

Regulator model number:

Voltage setpoints listed on regulator:

TABLE 3: Preliminary Charging System Check-OutCONDITION: CHECK FOR:

Low Voltage Output

Low battery state of charge. Load on system exceeds rated out-put of alternator.Faulty wiring or poor ground path.Faulty alternator or regulator.Wrong pulley installed.Wrong regulator installed.

High Voltage Output

Faulty regulator.Faulty alternator.

No Voltage Output

No energize signal at IGN terminal on regulator.Faulty alternator B+ terminal connection.Faulty alternator or regulator.

• Digital Multimeter (DMM)• Ammeter (digital, inductive)• Jumper wires

4. Determine battery type, voltage, and state of charge. Batteries must be all the same type. If batteries are discharged, recharge or replace batteries. Electrical system cannot be properly tested unless batteries are charged 95% or higher. See page 1 for details.

5. Connect meters to alternator:• Connect DMM red lead to alternator B+

terminal.• Connect DMM black lead to alternator B–

terminal.• Clamp inductive ammeter onto alternator B+

cable.6. Operate vehicle and observe charge voltage.

Charge voltage should increase and charge amps should decrease. Battery is considered fully charged when charge voltage is at regulator set point and charge amps remain at lowest value for 10 minutes.

If voltage is at or below regulator set point, allow charging system to operate for several minutes to normalize operating temperature. If charge voltage does not increase within 10 minutes, go to Chart 1 on page 6.

CAUTION If voltage exceeds 32 V, shut down system immediately. Damage to electrical system may occur if charging system is al-lowed to operate above 32 V for more than 3 sec-onds.

Check for OVCO Condition• Shut down vehicle and restart engine. If alternator

functions normally after restart, a no output condition was normal response of voltage regulator to high voltage condition.

• Inspect vehicle electrical system, including loose battery cables. If battery disconnects from system, it could cause high voltage condition in electrical system, causing OVCO circuit to trip.

• If you have reset alternator once, and electrical system returns to normal charge voltage condition, there may have been a one time, high voltage spike, causing OVCO circuit to trip.

• If OVCO circuit repeats cutout a second time in short succession and shuts off alternator, follow troubleshooting procedures in chart 2 on page 7.

Section B: Basic Troubleshooting

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Section C: Advanced Troubleshooting

Stop engine. Disconnect harness from alternator to regulator. If available, plug CEN A10-114 test tool into alternator only. Otherwise test directly through alternator-to-regulator harness pins. See Figure 6 below.

Chart 1: No Alternator Output – Test Charging Circuit• TEST MEASUREMENTS ARE TAKEN ON HARNESS PLUG AT ALTERNATOR. TAKING MEASUREMENTS FROM AN

EXTENDED HARNESS PLUG MAY AFFECT RESULTS. • FOR REMOTE-MOUNTED REGULATOR, CHECK CONDITION OF HARNESS FUSES BEFORE TROUBLESHOOTING.• BEFORE STARTING DIAGNOSTIC SEQUENCE, VERIFY THE FOLLOWING AND REPAIR/REPLACE IF NOT TO SPEC:

− BATTERIES FOR STATE-OF-CHARGE (25.0-28.0 V), CONDITION, AND SECURE CONNECTIONS. − MASTER BATTERY SWITCH FOR FUNCTION. − J1939 INTERCONNECT HARNESS FOR FUNCTION IF USED IN PARALLEL-OPERATION SYSTEM.

CAUTION MAKE SURE METER PROBES DO NOT TOUCH OTHER PINS AND CAUSE AN ARC THAT MAY DAMAGE PINS AND HARNESS WIRING.

MASTER BATTERY SWITCH ON, KEY ON, ENGINE ON: Test for battery voltage at B+ terminal on alternator to ground, then at IGN terminal on regulator to ground. If using A2-399 regulator, disconnect 3-pin Deutsch connector from regulator before starting engine and test IGN circuit for battery voltage from pin C of vehicle 3-pin harness to ground after engine is started. See Figure 7 below. Does battery voltage exist at both locations?

Yes No

MASTER BATTERY SWITCH ON, KEY ON, ENGINE OFF: Alternator/regulator must pass of all four tests.1. Battery voltage test: Set DMM to DC Voltage test. Connect DMM red lead to pin D. Connect DMM black lead to

pin C. Battery voltage should exist.2. Field coil resistance test: Set DMM on Ohms test. Field resistance between pins F and C should measure

nominal 1.0-1.5 ± 0.2 Ω. Field coil is defective if reading is less than 0.5 Ω or greater than 3 Ω.3. Field coil isolation test: Set DMM on Ohms test. Resistance between pins F and D should measure OL.4. Phase supply test: Set DMM to Diode test. Connect DMM black lead to pin E. Connect red lead to

alternator B+ terminal. DMM should read OL in this direction. Reverse leads. DMM should read diode voltage drop in this direction. Repeat for pin E and B‒ terminal. Tests should read OL in one direction and diode voltage drop in the other direction.

Alternator is faulty.Regulator is faulty.

Stop engine. Repair vehicle wiring as necessary. Run engine and re-test charging circuit. Is charging sys-tem performing properly?

System is operative.

No Yes

A = Not UsedB = Not UsedC = B-D = B+E = PhaseF = F+

Figure 6: Alternator-to-Regulator Harness Pin Designation and Inline Harness Test Tool

A

B C D E

F

A = D+ B = Phase out C = IGN

AB

C

Figure 7: Vehicle 3-Pin Regulator Harness Pin Designation (A2-399 only)

Yes No

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Chart 2: Test OVCO Circuit

Yes No

1. Unplug alternator-to-regulator harness from regulator. Set DMM to Ohms test.2. Connect DMM red lead to alternator harness pin F.3. Connect DMM black lead to alternator B‒ terminal. Does resistance read 1.0-1.5 ± 0.2 Ω?

Yes No

1. Connect DMM red lead to alternator harness pin F.2. Connect DMM black lead to alternator B+ terminal. Does resistance read OL?

Yes No

Replace existing regulator with known good regulator. Run engine. Does OVCO trip?

Alternator is faulty

Alternator is faulty

Alternator is faulty

Original regulator is faulty

Section C: Advanced Troubleshooting (CONT'D)

If you have questions about your alternator or any of these test procedures, or if you need to locate a Factory Authorized Service Distributor, please contact us at: C. E. Niehoff & Co.• 2021 Lee Street • Evanston, IL 60202 USA

TEL: 800.643.4633 USA and Canada • TEL: 847.866.6030 outside USA and Canada • FAX: 847.492.1242 E-mail us at service@CENiehoff.com